It can be found inside the Valentine Detective Agency building.
CASE: Old Friend in Need?
Client: Kenji Nakano
A Mister Kenji Nakano came into the office while you were out. He says he knows you, and that he needs your help again. I've never seen him before. Old client of yours? I tried looking through the archived cases, but... Nick, let's just say I'm glad I took over the bookkeepping.
Anyway, Mister Nakano said he wanted to talk with you personally about his case, but it didn't take the greatest detective in the Commonwealth to tell what was wrong. That worried, been-up-for-days look he was wearing tells me we've got another missing person case on our hands. Poor fella.
The Nakano Residence is up in the Northeast, near the coast. A small fishing house. He said that he and his wife will be waiting for you. I also told him about your new partner, in case one of you decides to go up there on your own.
Be careful, though, the coast is a pretty dangerous area. I think they might be all alone up there.
Hope you can help them,